In this study, the transport theorem of phonons and electrons is utilized to create a model to predict the thermal conductivity of composite materials with nano particles. By observing or assuming the particle displacement in the matrix, a physical model between particles and matrix can be built. Then, the composite material can be divided into several regions. The regions construct the thermal resistance network. In each unit, (I) represents the nano particle itself, (II) is the region of matrix between nano particles, and (III) is the region without affected by nano particles in the interested conduction direction. In each region, the phonon or electron scattering caused by boundaries, impurities, or U-processes was taken into account to calculate the thermal conductivity. The overall thermal conductivity then can be derived from the thermal resistance network. The model is used to predict the thermal conductivity for several composite materials with nano particles. It shows a pretty good agreement with previous studies in literatures. Based on the model, some discussions about particle size and volume fractionare also made.